First check whether High Availability (HA) is enabled for the VM or not, as HA will prevent any manual action such as the VM shutdown, stop, restart, or start because the main purpose of HA is for actions to be taken without user interaction. In order to manually perform any task for a VM, we need to disable HA for the VM, perform a task, and then re-enable HA. Also, if anything inside the guest VM is preventing it from shutting down, it will not respond to the GUI shutdown or restart option. In such cases, it is best to shutdown or restart from within the guest VM.